Mobile Stations (MS), also known as User Equipment (UE), wireless terminals and/or mobile terminals are enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The communication may be made e.g. between two mobile stations, between a mobile station and a regular telephone and/or between a mobile station and a server via a Radio Access Network (RAN) and possibly one or more core networks.
The mobile stations may further be referred to as mobile telephones, cellular telephones, laptops with wireless capability. The mobile stations in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another mobile station or a server.
The wireless communication system covers a geographical area which is divided into Radio Coverage Areas (RCA), e.g. radio cells. Each radio coverage area is served by a network node, or base station e.g. a Radio Base Station (RBS), which in some networks may be referred to as “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and terminology used. The network nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A radio coverage area is the geographical area where radio coverage is provided by the network node/base station at a base station site. One base station, situated on the base station site, may serve one or several radio coverage areas. The network nodes communicate over the air interface operating on radio frequencies with the user equipment units within range of the respective network node.
In some radio access networks, several network nodes may be connected, e.g. by landlines or microwave, to a Radio Network Controller (RNC) e.g. in Universal Mobile Telecommunications System (UMTS). The RNC, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural network nodes connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), network nodes, or base stations, which may be referred to as eNodeBs or even eNBs, may be connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
The 3GPP is responsible for the standardization of GSM, UMTS, LTE and LTE-Advanced. LTE is a technology for realizing high-speed packet-based communication that may reach high data rates both in the downlink and in the uplink, and is thought of as a next generation mobile communication system relative UMTS.
In the present context, the expressions downlink, downstream link or forward link may be used for the transmission path from the network node to the mobile station. The expression uplink, upstream link or reverse link may be used for the transmission path in the opposite direction i.e. from the mobile station to the network node.
GSM technology according to prior art, provides a synchronized and frame aligned Local Radio Environment (LRE) with unique Radio Resource (RR) assignment per mobile call within the local radio environment at any time, resulting in collision free radio resource utilization within the local radio environment with respect to combination of frequency and frame time slot number and in best case random collision behaviour towards radio resource utilization outside the local radio environment. To maintain this orthogonal radio resource utilization is comprised definitions as of the local radio environment area in terms of a number of radio coverage areas, constituting a cluster. Also comprised is synchronization and frame alignment within the local radio environment area. In addition is comprised allowing frequency hopping when using the same frequency hopping sequence for indexing and the same frequency table for all mobile calls within the local radio environment area. Furthermore, assigning unique radio resource per mobile call within the local radio environment area in terms of unique combination of frequency and frame time slot number where frequency is selected either explicitly or by use of an offset value against a frequency hopping sequence index, may be comprised.
FIG. 1 below shows an example of such an local radio environment covering three radio coverage areas, (RCA A, RCA B and RCA C) with unique radio resource assignment (RR 1 to RR 7) within the local radio environment, according to prior art. The method to assign a unique radio resource within the local radio environment may use either fixed frequencies or offset against a frequency hopping sequence index, so called Mobile Allocation Index Offset (MAIO) and assignment may be made firmly per radio coverage area, i.e. each frequency or offset value assigned to only one radio coverage area, or on call basis, i.e. each frequency or offset value may be used in several radio cells simultaneously but uniquely per frame time slot number. The technical prerequisite for a local radio environment is merely that each combination of frequency and frame time slot number is uniquely assigned to one mobile call within the local radio environment at a given time. An advantage with forming such local radio environment, i.e. clusters of radio coverage areas, is that the interference between radio coverage areas within the cluster may be controlled and thereby reduced by distributing the radio resources within the cluster appropriately.
Prior art GSM technology also provides means, which may be software controlled or manual, to form the local radio environments. Such clusters of radio coverage areas may be formed from a network wide pattern of radio coverage areas by merging radio coverage areas that have high expected signal interference, e.g. by analysing signal strength relations, or physical antenna orientation, and thus benefit from orthogonal radio resource planning, or by other somewhat similar manners. Different stop criteria for forming larger local radio environments may apply, from which one obvious is running out of unique radio resources within the local radio environment, given a capacity requirement per radio coverage area.
Prior art GSM technology, as described above, suffers from some limitations, such as e.g. local radio environment size limitation. Possibility to form a local radio environment covering a larger number of radio coverage areas is limited by the expected number of unique radio resources estimated per radio coverage area, i.e. the number of instant frequencies used per radio coverage area, implemented as number of transmitters intended for traffic channels. It limits the creation of larger areas benefiting from the controlled interference environment that comes with all traffic channels being synchronized and aligned.
Another limitation of the prior art GSM technology is call capacity limitation. The total theoretical call capacity within a local radio environment is limited by the number of unique radio resources that may be defined, given the number of frequencies and the number of frame time slots. Also, for systems using a policy of firmly assigned frequency domain resources per radio coverage area, the individual theoretical call capacity per radio coverage area is limited by the number of unique radio resource assigned to that radio coverage area, thus a rigid capacity distribution is obtained.